Avalanche Forecast
Issued: Feb 27th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Cornices.
ahanna,
Avalanche Canada
Watch for signs of instability in wind affected terrain. You may find reactive wind slabs on a variety of aspects as northwest winds relocate recent snow in a reverse loading pattern.
Summary
Confidence
Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.
Weather Forecast
Saturday night: Flurries bringing around 3 cm, freezing level 500 m. Light southwest wind below 2000m, strong northwest ridgetop wind.
Sunday: Light flurries bringing a trace of snow. Freezing level 1300 m. Light southwest wind below 2000m, strong west-northwest ridgetop wind.
Monday: 10-20 cm new snow. Freezing level 1300 m. Strong southwesterly winds affecting all elevations.
Tuesday: Flurries. Freezing level 700 m. Light to moderate southwest wind.
Avalanche Summary
Reports from Thursday and Friday show:
- Evidence of the previous natural storm cycle up to size 3 on north to east aspects 1500 to 2000 m.
- Good propagation in explosive triggered storm slabs to size 2 (Thursday).
- Storm/wind slabs have been reactive to human triggers around treeline to size 1.
- Cornices have been very reactive to explosives as well as remote human triggers, size 2-2.5.
Going forward:
- Wind loading patterns will likely reverse with northwest winds, forming reactive wind slabs in new features.
Snowpack Summary
20 cm of recent snow overlies a variety of old surfaces including facets, spotty surface hoar in wind sheltered areas around treeline, a sun crust on steep solar aspects and a rain crust below 1500 m. Upper level wind, having recently shifted northwest is likely transporting the recent snow into wind slabs in a reverse-loading pattern in exposed features at upper elevations. Older wind slabs formed by previous southwest winds may also remain reactive to human triggers.
Another weak layer buried in mid-February is composed of a crust, facets or spotty surface hoar depending on elevation/aspect, and is now down 50-80 cm. There have been no recent avalanches reported on this layer. Large triggers, such as an avalanche in motion, cornice fall, or intense loading from snow, wind and/or a rapid rise in temperature could awaken these deeper weak layers.
The mid and lower snowpack is well settled and strong in most areas.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Minimize your exposure time below cornices.
Problems
Wind Slabs
Ongoing upper level wind from the northwest is likely reverse-loading recent snow into reactive wind slabs in atypical terrain features.
Aspects: North, North East, East, South East, South, South West.
Elevations: All elevations.
Likelihood
Expected Size
Cornices
Cornices are large, looming, and require extra caution under the current conditions.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Feb 28th, 2021 4:00PM
